Cellular radio networks are increasingly used to provide a variety of communication and information services to users. In many cases communication networks coexist with each other in a given geographical area and simultaneously provide services to subscribers.
A cellular radio network generally uses a certain partition of the available spectrum for providing services. However, as the available spectrum is limited, the usage of the spectrum is normally subject to regulation and each communication network will have a certain partition of the spectrum allocated for usage. In this case it needs to be assured that the coexisting cellular radio networks, or in general any radio networks, do not interfere with each other above a certain tolerable level.
One straightforward approach to avoid interference between cellular radio networks is to exclusively allocate a certain partition of the spectrum in one geographical area. Each cellular radio network may then provide communication services in the allocated partition of the spectrum. Interference may be further reduced by guard bands introduced between the allocated partitions of the spectrum.
A frequency range allocated to a cellular radio network may be a continuous range of frequencies, or certain partitions of the spectrum may be combined to a frequency range for one cellular radio network. Therefore, a frequency range of a cellular radio network may include a single sequence of frequencies or multiple discontinuous sequences of frequencies, or a set of individual frequencies.
While this approach may work well up to a certain number of subscribers or up to a certain number of networks, in case the number of networks or subscribers needs to be further increased, the available spectrum may not suffice for introducing new cellular radio networks or providing services to further subscribers.
In this case it is desirable to be able to introduce a further cellular radio network in an geographical area already covered by at least one cellular radio network, wherein the introduced cellular radio network may reuse frequencies already used in the existing cellular radio network.